файл консультативной информации (РАСШИРЕННЫЙ РЕАЛЬНЫЙ ВРЕМЯ) (file advisory information (ADVANCED REALTIME))
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
posix_fadvise — file advisory information (ADVANCED REALTIME)
Синопсис (Synopsis)
#include <fcntl.h>
int posix_fadvise(int fd, off_t offset, off_t len, int advice);
Описание (Description)
The posix_fadvise() function shall advise the implementation on
the expected behavior of the application with respect to the data
in the file associated with the open file descriptor, fd,
starting at offset and continuing for len bytes. The specified
range need not currently exist in the file. If len is zero, all
data following offset is specified. The implementation may use
this information to optimize handling of the specified data. The
posix_fadvise() function shall have no effect on the semantics of
other operations on the specified data, although it may affect
the performance of other operations.
The advice to be applied to the data is specified by the advice
parameter and may be one of the following values:
POSIX_FADV_NORMAL
Specifies that the application has no advice to give on its
behavior with respect to the specified data. It is the
default characteristic if no advice is given for an open
file.
POSIX_FADV_SEQUENTIAL
Specifies that the application expects to access the
specified data sequentially from lower offsets to higher
offsets.
POSIX_FADV_RANDOM
Specifies that the application expects to access the
specified data in a random order.
POSIX_FADV_WILLNEED
Specifies that the application expects to access the
specified data in the near future.
POSIX_FADV_DONTNEED
Specifies that the application expects that it will not
access the specified data in the near future.
POSIX_FADV_NOREUSE
Specifies that the application expects to access the
specified data once and then not reuse it thereafter.
These values are defined in <fcntl.h>.
Возвращаемое значение (Return value)
Upon successful completion, posix_fadvise() shall return zero;
otherwise, an error number shall be returned to indicate the
error.
Ошибки (Error)
The posix_fadvise() function shall fail if:
EBADF The fd argument is not a valid file descriptor.
EINVAL The value of advice is invalid, or the value of len is
less than zero.
ESPIPE The fd argument is associated with a pipe or FIFO.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
The posix_fadvise() function is part of the Advisory Information
option and need not be provided on all implementations.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
posix_madvise(3p)
The Base Definitions volume of POSIX.1‐2017, fcntl.h(0p)
